1. Field of the Invention
The present invention relates to a screen printing apparatus, and more particularly to a screen printing apparatus which is structured such that a printing agent is not left within a screen hole of a mask after printing.
2. Description of the Prior Art
A screen printing apparatus is structured such that a mask is arranged on a plate to be printed such as a printed circuit board and the like, a printing agent such as a creamed solder and the like mounted on the mask is expanded by a squeegee, and a printing is performed at a predetermined position of the plate to be printed via a screen hole provided on the mask.
At a time of printing by the squeegee, a printing agent 103 such as a creamed solder and the like within a screen hole 102 of a mask 101 is taken out from the screen hole 102 only by an own weight of the printing agent 103 itself and an adhesive force as shown in FIG. 3 when the plate to be printed is peeled out from the mask in accordance with a downward movement of the plate to be printed such as the printed circuit board and the like, so that a power at a time of the printing agent being taken out therefrom is poor and there is a case in which the printing agent is attached to an inner surface of the screen hole 102 and left therein. Further, the printing agent gradually sticks thereto or is expanded around the screen hole at a back side thereof.
Further, there is a case in which the printing agent itself printed on a base plate lacks a sharp property. In this case, reference numeral 104 in the drawing denotes a plate to be printed such as a printed circuit board and the like.
Accordingly, it is necessary to frequently perform a cleaning of the mask while stopping the operation of a machine.